A multipurpose photoelectric reflectometer

Abstract

The multipurpose reflectometer was developed primarily to measure apparent reflectance, specular gloss, and trichromatic coefficients. These meas urements are useful in the ceramic, paint, text ile, paper, and chemical industries to indicate lightness, gloss, and color of finished articles. I n the reflectometer, two light beams from a single source are directed along separate p aths to two barrier-layer photocells. Various types of these photocells were studied to find which could be used most advantageously. The reflectometer employs a s ubstitution null method and requires a galvanometer to indicate equality of the currents generated by the two photocells. For each sample tested, there is a photometric adjustment to restor e equality of the currents. The amounts of photometric adjustment are m easured on the direct-reading scales , one of which is used for apparent reflectance and the other for spec ul a r gloss. Because of its high precision, the instrument is well suited for measuring small differences in apparent reflectance, gloss, or color of nearly identical samples. However, for grea t est accuracy, it is necessary to correct the scale readings by calibration.

Weather resistance of porcelain enamels exposed for seven years

“…3 . Specular Gloss Specular-gloss measurements were made on each panel at the exposure site, by using the Hunter Multipurpose Reflectometer [7] adjusted for a 45° angle of incidence. Measurements were made at two fixed locations near the center of the panel immediately after the cleaning operation, which consisted of (a) washing with a warm I -percent solution of trisodium phosphate, (b) thoroughly rinsing with tap water, and (c) drying in air.…”

Weather resistance of porcelain-enameled iron structural units

“…They were first washed with a warm I-percent solution of trisodium phosphate, thoroughly rinsed in hot tap water, and dried in air. Specular-gloss measurements were made with the Hunter Multipurpose Reflectometer [5] at two fixed locations near the center of the surface to be exposed. R eflectance values with blue, green, and amber filters were obtained with the same instrument at the two lower corners of each specimen as a means of obtaining a permanent record of the initial color.…”

The Improvement of Luster of Cotton

“…These have been described by Hunter [ 18,19] so that only a few practical notes on the specific application to cotton materials are required.…”

“…The fixed-angle reflectometer is designed for use in several different ways [18], two of which are of importance in measuring luster characteristics. For measurement of 45°, 0° reflectance, the instrument is calibrated with working standards, usually enamel on steel, which have themselves been standardized in terms of magnesium oxide as 100.…”